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Tunneling Shaft sinking and drifting.doc
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2.18. Skim the text once again and fill in the table. Discuss the results you have obtained with your group-mates.

Trenchless technology

advantages

disadvantage

1.

2.

3.

4.

2.19. Click here to watch the video about how trenchless piper replacement technology works.

http://www.youtube.com/watch?v=Q6I06X-FBaM

2.20. Translate the following text in written form with a dictionary. Try to manage within 15 minutes. Shallow-buried Tunnel or Soft Soil Tunnel

Shallow tunnels are of a cut-and-cover type (if under water of the immersed-tube type). Deep tunnels are excavated, often using a tunneling shield. For intermediate levels, both methods are possible.

Cut-and-cover method

Cut-and-cover is a method of tunnel construction where a trench is excavated and roofed over. Strong supporting beams are necessary to avoid the danger of the tunnel collapsing.

Shield method

The shield method uses one or two shields (large metal cylinder) to cut out a tunnel through the soft ground.

A rotating cutting wheel is located at the front end of the shield. Behind the cutting wheel is a chamber where, depending on the type of the TBM, the excavated soil is either mixed with slurry (called slurry TBM) or left as is (earth pressure balance or EPB shield). Systems for removal of the soil (or the soil mixed with slurry) are also present.

Behind the chamber is a set of hydraulic jacks supported by the finished part of the tunnel which are used to push the TBM forward. Once a certain distance has been excavated (roughly 1.5-2 meters), a new tunnel ring is built using the erector. The erector is a rotating system that picks up pre-cast concrete segments and places them in the desired position.

Behind the shield, inside the finished part of the tunnel, several support mechanisms can be found that are part of the TBM: dirt removal, slurry pipelines if applicable, control rooms, and rails for transport of the precast segments, etc.

2.21. Read and summarize the text “Underwater Tunnel” using expressions (page 67). Underwater Tunnel

Immersed-tube method

An immersed tube method is technique of underwater tunneling used principally for underwater crossings. The first tunnel constructed with this method was the Shirley Gut Siphon, a six foot sewer main laid in Boston, Massachusetts in 1893. Then this method was pioneered by the American engineer W.J. Wilgus in the Detroit River in 1903 for the construction of a tunnel to carry traffic (Michigan Central Railroad). Wilgus dredged (драгировать) a trench in the riverbed, floated (переправлять) segments of steel tube into position, and sank (погружать) them; the segments were locked together by divers and pumped out and could then be covered with excavated material. Though the technique has been refined since, it remains basically the same and has been used for many underwater tunnels all over the world.

The segments of the tube may be constructed in one of two methods. In the United States, the preferred method has been to construct steel or cast iron tubes which are then lined with concrete. This allows use of conventional shipbuilding techniques, with the segments being launched (спускать на воду) after assembly in dry docks. In Europe, reinforced concrete box tube construction has been the standard; the sections are cast in a basin which is then flooded to allow their removal.

A major advantage of this method is that, once the new section has been connected, interior work is conducted in free air, avoiding the high cost and major risk of operating a large shield under high air pressure. Moreover, the immersed-tube method is usable in water deeper than is possible with the shield method, which essentially is restricted to less than 100 feet of water by the maximum air pressure at which workers can safely work.

The disadvantages of this method include:

- The tunnel is partly exposed on the river / sea bed, risking a sunken ship / anchor strike,

- Direct contact with water necessitates careful waterproofing design around the joints,

- The segmental approach requires careful design of the connections,

- Environmental impact of tube and underwater embankment (насыпь) on existing channel / sea bed.

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